(a) Technical Field
The present invention relates to an apparatus and method for controlling switching devices for a DC motor. More particularly, it relates to an apparatus and method for controlling switching devices for a DC motor, which can control dead-time using a hardware circuit design.
(b) Background Art
Typically, a three-phase pulse width modulation (PWM) inverter is used as a power converter for supplying a three-phase alternating current to a DC motor having a high power output in a hybrid vehicle. In a half-bridge circuit for driving the DC motor, two metal-oxide-semiconductor field-effect transistor (MOSFET) switching devices can switch independently between each other. However, when the two devices are turned on at the same time, the DC output is short-circuited, and a large amount of current flows therethrough, which is capable of destroying the devices. Accordingly, the switching devices operate in a complementary switching manner such that the on/off states of the two devices are opposite of each other at any given time.
Nevertheless, during on/off switching of the two devices, there is a possibility that the two devices may be both on at the same time due to a difference in propagation delay time of gating signals and because of a difference between the time during which the semiconductor switching device is turned on and the time during which the semiconductor switching device is turned off.
In particular, the time during which the switching device is turned off is always longer than the time during which the switching device is turned on, and thus, when the gating signals for switching the on/off states of the two devices are applied at the same time, the two devices may be both on at the same time thereby causing an unwanted short circuiting incident, thus resulting in power loss.
As such, in order to prevent this unwanted short circuiting incident during the on/off switching of the two devices, a turn-on signal is applied to the device to be turned on after a predetermined time has elapsed, thereby ensuring the other devices is turned off appropriately. The time during which the turn-on signal is delayed is called the dead-time.
Typically in vehicles, a controller provided with a microcontroller controls the dead-time via a software program. However, if the controller is not equipped with a microcontroller, the dead-time cannot be controlled via a software program, and thus it is necessary to provide appropriate countermeasures.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.